Process for increasing the melt strength of polypropylene

ABSTRACT

A process for modifying a polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator wherein said initiator is selected from the group defined by formula (1), wherein R is selected from the group consisting of optionally substituted C 1  to C 18  acyl, optionally substituted C 1  to C 18  alkyl, aroyl defined by formula (2), and compounds of formula (3), wherein U, V, X, Y, Z, U′, V′, X′, Y′ and Z′ are independently selected from the group consisting hydrogen; halogen; C1-C18 alkyl; C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula (4), and wherein T is alkylene.

This application is the U.S. national phase of International ApplicationPCT/AU99/00036, filed Jan. 19, 1999.

The press invention relates to polypropylene homopolymers andcopolymers. In particular, the present invention relates to a processfor increasing the melt strength and/or the extensional melt viscosityof said polymers by melt phase processing.

The melt strength and extensional viscosity of linear or straight chainpolymers, such as polypropylene, decreases rapidly with temperature. Bycontrast, polymers such as low density polyethylene which are highlybranched retain relatively high melt strengths and extensionalviscosities. It is generally understood that the difference in meltstrengths and extensional viscosities is attributable to the presence oflong chain branching in polymers such as low density polyethylene. Longchain branching allows a greater degree of chain entanglement.

A number of methods for increasing the melt strength/extensionalviscosity of polypropylene and related polymers through the introductionof branching or a limited degree of crosslinking in a process involvingreactive extrusion have been proposed and are summarised in a recentpaper by Wang et al. (Wang, X., Tzoganakis, C., and Rempel, G. L., J.Appl. Polym. Sci., 1996, 61, 1395). One such process involves thereactive extrusion of polypropylene with a polyfunctionalmonomer/initiator combination. For example, the use of pentaerythritoltriacrylate in combination with 2,5-dimethyl-2,5-di(t-butylperoxy)hexane(DHBP).

White (U.S. Pat. No. 5,578,682) has disclosed the use of variouspolyunsaturated crosslinking agents (for example, bismeleimidederivatives) in combination with free radical initiators to achieve anincrease in the melt strength various polymers.

It is well known that the melt phase processing of polypropylene leadsto mechanochemical degradation. The processing of polypropylene in thepresence of free radical initiators provides an increased rate ofdegradation. This controlled degradation of polypropylene is usedcommercially for the production of controlled rheology resins havingreduced polydispersity and reduced die swell (Lambla, M. inComprehensive Polymer Science, Pergamon, New York 1992, vol Suppl. 1, p619; Hogt, A. H., Meijer, J., Jelinic, J. in Reactive Modifiers forPolymers, Al-Malaika, S. Ed., Chapman & Hall, London, 1996, p 84.). Thedegradation of polypropylene as described therein results in a loweringof melt strength.

The batch modification of polypropylene to produce crosslinked(insoluble) polypropylene by treatment with peroxides is described byBorsig et al. (Borsig, E., Fiedlerova, A., Lazar, M. J., Macromol. Sci,Chem., 1981, A16, 513). Initiators which produce benzoyloxy radicals orphenyl radicals are described as being more efficient in inducingcrosslinking or grafting than those which produce t-butoxy or alkylradicals. The process requires the use of high levels of peroxide. Theuse of polyfunctional monomers as coagents to retard degradation andenhance crosslinking is described by Chodak, I.; Fabianova, K.; Borsig,E.; Lazar, M. Agnew. Makromol. Chem., 1978, 69, 107.

DeNicola (EP 384331A2) has disclosed a means to produce a branchedpropylene polymer material showing a net increase in the weight averagemolecular weight by solid state modification of predominantly isotacticsemi-crystalline linear polypropylene. The process described inEP384331A2 involves blending peroxides with short half lives (eg peroxydicarbonates) with linear propylene polymer in a mixing vessel attemperatures from 23° C. to 120° C. in an inert atmosphere andcontinuing to mix for a period of time until the peroxide decomposes andpolymer fragmentation and branching occurs without significant gelationof the polymer. DeNicola states that at temperatures greater than 120°C. no branching or melt strength enhancement is achieved.

U.S. Pat. No. 5,464,907 teaches that certain unsaturated maleate oritaconate derived peroxides may be used to induce grafting inpolypropylene and α-olefin copolymers. They report that use of otherperoxides generally results in chain degradation.

Polypropylene is also known to undergo substantial degradation duringmelt phase grafting of monofunctional monomers, for example maleicanhydride and glycidyl methacrylate. It has also been reported that thedegradation that accompanies grafting of these monomers to polypropylenemay be reduced by the addition of relatively high concentrations ofcertain comonomers including styrene (see, for example Sun, Y.-J., Hu,G.-H., and Lambla, M., Angew. Makromol. Chem, 1995, 229, 1; Chen, L-F.,Wong, B. and Baker, W. E. Polym. Eng. Sci. 1996, 36, 1594.) Sun et al.report that there is degradation (as indicated by an overall decrease inmolecular weight) when styrene alone is grafted onto polypropylene evenwhen a relatively high concentration is used (4 moles/100 g PP). Either2,5-dimethyl-2,5-(t-butylperoxy)hex-3-yne or2,5-dimethyl-2,5(t-butylperoxy-hexane(DHBP) was used as the initiator inthese experiments.

We have found that melt mixing polypropylene homopolymer orethylene-polypropylene copolymer in the presence of a suitable initiatorprovides one or more of the following: increased melt strength;increased extensional viscosity; increased molecular weight; andbroadened molecular weight distribution.

According to the present invention there is provided a process formodifying a polypropylene (co)polymer wherein said process comprisesmelt mixing the polypropylene (co)polymer in the presence of aninitiator wherein said initiator is selected from the group defined byformula 1:

wherein R is selected from the group consisting of optionallysubstituted C₁ to C₁₈ acyl, optionally substituted C₁ to C₁₈ alkyl,aroyl defined by formula 2,

and groups of formula 3,

wherein U, V, X, Y, Z, U′, V′, X′, Y′ and Z′ are independently selectedfrom the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl,aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4,

and wherein T is alkylene.

Advantageously the thus formed modified polypropylene may be obtainedwithout the associated production of significant and detrimental amountsof gels.

Polymers suitable for use in the present invention include a widevariety of polypropylene homopolymers, copolymers and blends containingone or more polypropylene homopolymers and/or copolymers.

Suitable polypropylene homopolymers include isotactic polypropylene,atactic polypropylene and syndiotactic polypropylene. Commercialisotactic polypropylene having a proportion of meso/dyads of greaterthan 90% is preferably used in the process of the present invention.Isotactic polypropylene is a semi-crystalline polymer having a number ofproperties which have made it one of the most widely used commercialpolymers. These properties include heat resistance, stress crackingresistance, chemical resistance, toughness, and low manufacturing costs.However, the melt strength of isotactic polypropylene as measureddirectly by extensional viscosity or use of a commercial melt strengthtester or indirectly by more qualitative measures such as drop time ordie swell ratio is relatively low. This relatively low melt strengthlimits the use of polypropylene in applications such as foam extrusion,thermoforming and film blowing. In order to use polypropylene in suchapplications it is necessary to employ sophisticated processingequipment. The present invention now permits this already widely usedcommercial polymer to be used in an even wider range of applications.

Polypropylene copolymers include copolymers of propylene and othermonomers with such other monomers being present preferably in amounts ofup to 10% wt/wt. A preferred comonomer is ethylene.

The present invention is also applicable to other polymers comprisingα-olefin monomers. It is preferable that any such α-olefins are presentin the polymer to be modified in amounts in excess of 90% wt/wt.α-olefins include propene, 1-butene, 1-pentene and 1-hexene.

The initiators for use in the present invention may be selected from thegroup defined by formula 1.

wherein R is selected from the group consisting of optionallysubstituted C₁ to C₁₈ acyl, optionally substituted C₁ to C₁₈ alkyl,aroyl defined by formula 2,

and groups of formula 3,

wherein U, V, X, Y, Z, U′, V′, X′, Y′ and Z′ are independently selectedfrom the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl,aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4,

and wherein T is alkylene.

The alkyl, including acyl and alkoxy, groups included in the initiatorsof formula 1 may include hetero atoms within the carbon chain (egpolyalkylene oxide) and may be branched or unbranched and may besubstituted with one or more groups such as with alkyl, aryl, alkoxy orhalogen substituents.

Without wishing to be bound by theory, it is believed that the aroyloxyradical of formula 5

where U, V, X, Y and Z are as hereinabove defined, provide thesurprising increase in melt strength. Other compounds which generatethese aroyloxy radicals may also be used in the present invention.

A preferred class of initiators of formula 1 are diaroyl peroxides offormula 6.

where X, Y, Z, U, V, X′, Y′, Z′, U′, V′ are independently selected fromthe group consisting of hydrogen and C₁-C₁₈ alkyl where at least one ofX, Y, Z, U, V and X′, Y′, Z′, U′, V′ are not hydrogen.

Diaryl peroxides of formula 6 include Dibenzoyl peroxide,o,o′-Bis(methylbenzoyl) peroxide, p,p′-Bis(methylbenzoyl) peroxide,M,M′-Bis(methylbenzoyl) peroxide, o,m′-Bis(methylbenzoyl) peroxide,o,p′-Bis(methylbenzoyl) peroxide, m,p′-Bis(methylbenzoyl) peroxide,Bis(ethylbenzoyl) peroxide (all isomers), Bis(propylbenzoyl) peroxide(all isomers), Bis(butylbenzoyl) peroxide (all isomers),Bis(pentylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide(all isomers), Bis(heptylbenzoyl) peroxide (all isomers),Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide(all isomers), Bis(methoxybenzoyl) peroxide (all isomers),Bis(ethoxybenzoyl) peroxide (all isomers), Bis(propoxybenzoyl) peroxide(all isomers), Bis(butoxybenzoyl) peroxide (all isomers),Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl)peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers),Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl)peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers),Bis(fluorobenzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide(all isomers), Bis(dimethylbenzoyl) peroxide (all isomers),Bis(trimethylbenzoyl) peroxide (all isomers),Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tertbutoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide (all isomers),Bis(2,6-dimethyl-4-trimethysilyl benzoyl) peroxide and isomers,2,2′(dioxydicarbonyl) bis—Benzoic acid dibutyl ester where the term “allisomers” refers to any variation in the position of the ring substituentas well as the structure of the substituent itself i.e. for propyl;n-propyl and isopropyl.

Examples of aromatic peresters of formula 1 include the following:tert-butyl perbenzoate, tert-butyl (methyl)perbenzoate (all isomers),tert-butyl (ethyl)perbenzoate (all isomers), tert-butyl(octyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (allisomers), tert-amyl perbenzoate, tert-amyl (methyl)perbenzoate (allisomers), tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl(octyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (allisomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl(octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate(all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl(methyl)perbenzoate (all isomers), 2-ethylhexyl (ethyl)perbenzoate (allisomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl(nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (allisomers), 2-ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl(octyloxy)perbenzoate (all isomers), 2-ethylhexyl (nonyloxy)perbenzoate(all isomers)

The initiators for use in the present invention also include compoundsof formula I where at least one of U, V, X, Y, Z, U′, V′, X′ Y′ and Z′is a moiety of formula 4 where R is as defined above. Preferably thereis no more than one moiety of formula 4 per aromatic ring. Suchinitiators are di or higher functional peroxides and may includepolymeric peroxides such as Bis (tertbutylmonoperoxy phthaloyl) diperoxyterephthalate, Bis (tertamylmonoperoxy phthaloyl) diperoxy terephthalatediacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide,dibenzoyl terephthaloyl diperoxide,Poly[dioxycarbonyldioxy(1,1,4,4-tetramethyl-1,4-butanediyl)] peroxide.

It is described that the initiators are selected such that it has anappropriate decomposition temperature (half life), solubility, andreactivity and such that the groups R, T, X Y, Z, U, V, X′, Y′, Z′, U′,V′ give no adverse reaction under the conditions of the process.Preferred peroxides will have a 0.1 hour half life in the range 100-170°C.

The amount of initiator used in the process of the present inventionshould be an effective amount to achieve the desired increase in meltstrength. Melt strength is considered in the art to be an indication oflong-chain branching in polyolefins. It is preferable in the process ofthe present invention that long-chain branching predominates overcrosslinking in the reaction between the initiator and the polypropylene(co)polymer. Crosslinking of the polypropylene (co)polymer may result inthe formation of gels which disrupt the appearance of the polypropylene(co)polymer. In the process of the present invention it is desirable tocontrol the degree and distribution of crosslinking and keep the levelof crosslinking as uniform and as low as necessary to produce thedesired effects. The amount of crosslinking which occurs in thepolypropylene (co)polymer is dependant upon the amount of initiator meltmixed with the polypropylene (co)polymer. The amount of crosslinking isalso dependent upon the degree of mixing as any regions high ininitiator concentration will result in excessive localised crosslinkingand the formation of gels. It is desirable that good distributive anddispersive mixing be employed to promote even distribution of theinitiator in the polypropylene (co)polymer so as to minimise thevariation in initiator concentration throughout the polypropylene(co)polymer and reduce the likelihood of the formation of gels.

Preferably the initiator will be present in the range of from 0.004 to0.25 moles of initiator per kg of the polypropylene homopolymer orcopolymer (polypropylene (co)polymer). The mole preferred range beingfrom 0.006 to 0.10 moles of initiator per kg. of the polypropylene(co)polymer and even more preferred range being from 0.01 to 0.05 molesof initiator per kg of the polypropylene (co)polymer.

The initiator is preferably introduced into the polymer melt directly,either neat (as a powder or a liquid), dispersed or dissolved in asuitable medium (for example, dissolved in 2-butanone) or adsorbed onpolymer pellets or powder which are added as a masterbatch. It isdesirable that the initiator is rapidly mixed with the polymer melt at arate in keeping with the half life of the initiator at the processingtemperature of the polypropylene (co)polymer.

The initiator may be added either alone, or along with the polypropylene(co)polymer, or with any other polymer, additive or filler, so that thepolymer melts and mixes with the initiator as it is decomposing. Whenthe initiator is fed to the main feed throat of the extruder it ispreferred to have a barrel temperature which is relatively low in theregion adjacent to the main feed throat and increases towards the die toprevent premature decomposition of the peroxide.

Preferably the initiators for use in the present invention are selectedfrom the group consisting of Dibenzoyl peroxide, o,o′-Bis(methylbenzoyl)peroxide, p,p′-Bis(methylbenzoyl) peroxide, o,o′-Bis(methylbenzoyl)peroxide, o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl)peroxide, m,p′-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide(all isomers), Bis(propylbenzoyl) peroxide (all isomers),Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide(all isomers), Bis(hexylbenzoyl) peroxide (all isomers),Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide(all isomers), Bis(nonylbenzoyl) peroxide (all isomers),Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide(all isomers), Bis(propoxybenzoyl) peroxide (all isomers),Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyl) peroxide(all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers),Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl)peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers),Bis(chlorobenzoyl) peroxide (all isomers), Bis(fluorobenzoyl) peroxide(all isomers), Bis(bromobenzoyl) peroxide (all isomers),Bis(dimethylbenzoyl) peroxide (all isomers), Bis(trimethylbenzoyl)peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tertbutoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide (all isomers),Bis(2,4-dimethyl-6-trimethysilyl benzoyl) peroxide and isomers tert-amylperbenzoate, tert-amyl (methyl)perbenzoate (all isomers), tert-amyl(ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (allisomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl(methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (allisomers), tert-amyl (nonyloxy)perbenzoate (all isomers), Bis(tertamylmonoperoxy phthaloyl) diperoxy terephthalate, diacetylphthaloyl diperoxide, dibenzoyl phthaloyl diperoxide,bis(4-methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl diperoxide and dibenzoyl terephthaloyl diperoxide.

More preferably the initiators are selected from the group consisting ofdibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, M,M′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide,m,p′-Bis(methylbenzoyl) peroxide.

The initiators may optionally be used in combination with one or moremonomers.

Preferably the one or more monomers are selected from the groupconsisting of monene monomer. It will be understood by those skilled inthe art that by the term “monoene monomer” it is meant a monomer havinga single reactive double bond.

The preferred monoene monomer(s) or mixtures thereof include vinylmonomers of structure CH₂═CHX where X is chosen so as to confer thedesired reactivity and solubility. More preferred monomers includestyrene. The amount of monomer will preferably be up to 5 times thetotal moles of initiator added to the polypropylene (co)polymer. Themost preferred range being 1 to 4 times the total moles of initiatoradded to the polypropylene (co)polymer.

The monomer may be added with the polypropylene (co)polymer or it can beadded prior to the initiator, with the initiator or subsequent to theinitiator. However it is preferred to have the monomer mixed anddispersed into the polymer melt before the initiator has substantiallydecomposed. The monomer is preferably introduced into the polymer meltdirectly, either neat (as a powder or a liquid), dispersed or dissolvedin a suitable medium (for example, dissolved in 2-butanone) or adsorbedon polymer pellets or powder which are added as a

Preferred initiators for use in combination with monomers includeDibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, M,M′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide,m,p′-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (allisomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl)peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers),Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide(all isomers), Bis(octylbenzoyl) peroxide (all isomers),Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide(all isomers), Bis(ethoxybenzoyl) peroxide (all isomers),Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide(all isomers), Bis(pentoxybenzoyl) peroxide (all isomers),Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl)peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers),Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide(all isomers), Bis(fluorobenzoyl) peroxide (all isomers),Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide(all isomers), Bis(trimethylbenzoyl) peroxide (all isomers),Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tert-butoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide (all isomers),Bis(2,4-dimethyl-6-trimethylsilyl benzoyl) peroxide and isomers,2,2′(dioxydicarbonyl) bis—Benzoic acid dibutyl ester, tert-butylperbenzoate, tert-butyl (methyl)perbenzoate (all isomers), tert-butyl(ethyl)perbenzoate (all isomers), tert-butyl (octyl)perbenzoate (allisomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-amylperbenzoate, tert-amyl (methyl)perbenzoate (all isomers), tert-amyl(ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (allisomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl(methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (allisomers), tert-amyl (nonyloxy)perbenzoate (all isomers), 2-ethylhexylperbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers),2-ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl(octyl)perbenzoate (all isomers), 2-ethylhexyl (nonyl)perbenzoate (allisomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2-ethylhexyl(ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perbenzoate(all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers), Bis(tertbutylmonoperoxy phthaloyl) diperoxy terephthalate, Bis(tertamylmonoperoxy phthaloyl) diperoxy terephthalate diacetyl phthaloyldiperoxide, dibenzoyl phthaloyl diperoxide, bis(4 methylbenzoyl)phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, dibenzoylterephthaloyl diperoxide andPoly[dioxycarbonyldioxy(1,1,4,4-tetramethyl-1,4-butanediyl)] peroxide.

Advantageously initiators may be selected to avoid undesirableby-products. In certain applications, it may be desirable to avoid theuse of initiators which generate benzene. For example di toluoylperoxides (bis methyl benzoyl peroxides) may be used in preference todibenzoyl peroxide.

The processability and other properties of the product may be improvedby a chain scission step following the initial polymer modificationstep. This may be carried out by:

-   -   a) adding one or more additional initiators with or subsequent        to the first initiator addition;    -   b) the use of high shear mixing;    -   c) the use of high temperatures;    -   d) the use combination is of one or more of (a)-(c) above.

This additional step in the production of a polymer enables tailoringthe properties of the product to the requirements of the desiredapplication. For example, by this two stage process it is possible toproduce materials with similar melt viscosity to the base polymer but asubstantially increased melt strength. Use of the single stage processgenerally provides both an increase in melt strength and an increase inmelt viscosity (see examples)

One or more additional initiators may be added to the polypropylene(co)polymer during the modification process either with or subsequent tothe initiator and monomer addition. The additional initiator is typicaladded to give chain scission of the polypropylene (co)polymer so as todecrease the melt viscosity and improve the processability of themodified polypropylene (co)polymer. The additional initiator should beintroduced to the polymer melt after the first initiator or have asufficiently long half-life relative to the first initiator such thatits decomposition can be staged to occur after the initial polymermodification process. In some instances a polypropylene (co)polymermodified in accordance with the present invention may have a MFI<1 g/10min. With use of the additional initiator an MFI>1 g/10 min may beachieved. The additional initiator may be selected from the groupconsisting of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP), dicumylperoxide (DCP), t-butyl peroxy-2-ethylhexonate(TBEH), and dilaurylperoxide (DLP) or any other peroxide which may result in the overallchain scission of the polypropylene (co)polymer during melt processing.For example in the absence of the monoene monomers, t-butylperoxybenzoate or other non-preferred initiators for use in the presenceof the monomer may be preferably added as the additional initiator.While the improvement in processability through chain scission normallyresults in some decrease in the melt strength/extensional viscosity ofthe modified polypropylene (co)polymer, the melt strength/extensionalviscosity may still be acceptable, and improved over the unmodifiedpolypropylene (co)polymer.

It is possible to combine the process of the present invention withother processes of polymer modification or with, for example, theaddition of fillers, additives or stabilisers, or blending with otherpolymers.

In the process of the present invention the polypropylene (co)polymer ismelt mixed in the presence of initiator and optionally a monomer. Meltmixing may be carried out by any convenient means capable of mixing thepolypropylene (co)polymer at temperatures above the melting point of thepolypropylene (co)polymer.

Suitable apparatus for melt mixing the polypropylene (co)polymer includecontinuous and batch mixers. Suitable mixing equipment includesextruders such as single screw and twin screw extruders, static mixers,cavity transfer mixers and combinations of two or more thereof. It ispreferred that the melt mixing is conducted in either a co- orcounter-rotating twin screw extruder.

The barrel set temperatures are preferably in the range 80-280° C.Typical melt temperatures are in the range 170-290° C.

In order to optimise the melt extensional viscosity, the preferred melttemperatures are in the range 160° C. to 220° C. This rage providesoptimal properties whilst minimising the amount of chain scission whichoccurs during processing. However, in some cases it may be desirable touse higher temperatures such as in the venting/discharge sections ofsingle screw or twin screw extruders or to induce some chain scission inorder to decrease the molecular weight of the modified polypropylene(co)polymer and improve the processability of the modified polypropylene(co)polymer.

Typically, the die temperatures are in the range 180-290° C.

Preferably the extrusion conditions are adjusted so that thepolypropylene (co)polymer, initiator/monomer mixture are conveyed asquickly as possible into the melting/mixing zone to maximise the meltphase reaction (eg for twin screw extruders—high throughput rates,higher screw seeds under starve fed conditions). It is more preferredthat the additives are added to and mixed with molten polypropylene(co)polymer to further enhance the melt phase reaction. Preferablyresidence times in the range of from 10 seconds to 5 minutes areselected depending upon the temperature profile, throughput rate andinitiator levels. More preferred residence times are in the range offrom 15 seconds to 120 seconds.

Vacuum venting can be applied to remove volatile by-products, solventsand/or excess monomer.

While not wishing to be limited by theory, it is believed that theeffectiveness of the present invention is determined by three factors:

-   (a) The rate and specificity of the reaction of the aroyloxy or the    derived phenyl radicals or substituted phenyl radicals with    polypropylene, and the monomer if present. It is believed that the    aroyloxy, phenyl or substituted aroyloxy or phenyl radicals show    less specificity for abstraction of tertiary vs. secondary or    primary hydrogens than do, for example, alkoxy or alkyl radicals.-   (b) The initiator half-life. Use of an initiator with a short    initiator half-life will generate a locally high concentration of    radicals thus increasing the likelihood of radical combination    events.-   (c) The solubility characteristics of the initiator in the polymer    melt.

Without wishing to be bound by theory, peroxides that generate aroyloxyor aryl radicals (for example benzoyloxy, p-toluouloxy) are preferredover those that generate alkoxy radicals (for example, t-butoxy radical,cumyloxy radical). It is believed and supported in the literature thatthe latter class of peroxides promote chain scission under the meltmixing conditions. While not wishing to be bound by the mechanism, it isbelieved that this effect is due to the specificity shown by the alkoxyradicals as opposed to the aroyloxy or aryl radicals generated by theperoxides of structure 1. Furthermore we believe that peroxides whichgenerate both alkoxy and aroyloxy or aryl radicals (for example, t-butylperbenzoate) show intermediate behaviour. It is believed that theypromote less chain scission than peroxides which generate only alkoxyradicals (for example, dialkyl peroxides) when used alone and can beused to advantage in systems where a monomer coagent is employed.Preferred peresters are thus those which generate alkoxy radicals whichare not active in hydrogen abstraction (for example t-amyl perbenzoate).

Similarly, it is believed, without wishing to be bound by theory, thatthe effectiveness of the monomer is determined by:

-   (a) The solubility of the monomer in the polymer melt. For example,    styrene is known to be soluble in molten polypropylene.-   (b) The reactivity of the monomer towards polypropylene derived    radicals.-   (c) The propensity for the radical formed by addition of monomer to    give combination or addition (which leads to branch or crosslink    formation) vs. disproportionation or hydrogen abstraction. It is    known that the benzylic radicals give predominantly combination and    have low (with relation to other radicals) tendency to abstract    hydrogen.

Other initiators and monomers that meet the above criteria may also beused to advantage in the present invention.

Surprisingly, the process of the present invention results in apolypropylene (co)polymer with substantially increased melt strength. Wehave found that it is possible with the present invention to obtain apolypropylene (co)polymer which has a melt strength at least 25% greaterthan the melt strength of the base polymer. We have also found that itis possible to obtain an increase in melt strength of greater than 100%for a number of the polypropylene (co)polymers produced in accordancewith the process of the present invention. Increases in melt strengthwere assessed using a Gottfert-Rheotens melt strength tester operatedwith a roller acceleration of 1.2 cm/sec² measuring the melt strength ofa 2 mm strand of molten polypropylene (co)polymer (melt temperature of210° C.) which is fed to the Gottfert tester at ˜4 g/min.

In a further aspect of the present invention there is provided amodified polypropylene (co)polymer produced according to the processdescribed herein, wherein said modified polypropylene (co)polymerpreferably has a melt strength at least 25%, and more preferably atleast 100%, greater than the unmodified polypropylene (co)polymer.

The polypropylene (co)polymers produced according to the process of thepresent invention also may provide a significant increase in long-chainbranching. Long-chain branching may be assessed by the Dow RheologyIndex. Advantageously, the modified polypropylene (co)polymers maydemonstrate a Dow Rheology Index (DRI) of greater than 1, preferably atleast 2 and most preferably greater than 50.

The process of the present invention may also be used to increase themelt elasticity of a polypropylene (co)polymer.

Advantageously, the process of the present invention also provides ameans to alter the molecular weight, molecular weight distributionand/or degree and length of branching of polypropylene,ethylene-propylene copolymers, and analogous α-olefin copolymers with orwithout altering the melt strength of said polymers by melt processing.

The process of the present invention may provide a means to generallyincrease the molecular weight and broaden the molecular weightdistribution and/or introduce branching of the polypropylene(co)polymer. This will not always equate to significant increases in themelt strength or extensional viscosity of the polymer that is beingmodified eg modification of a lower molecular weight polymer to broadenthe molecular weight and/or induce shorter branches. Such a product maynot necessarily demonstrate a high melt strength, but may demonstrateother desirable properties, for example improved filler uptake,mechanical properties, surface properties, thermal and morphologicalproperties.

The modified polypropylene (co)polymer produced by the process of thepresent invention may be used either neat or blended with anotherpolymer or other additives to provide the desired balance of propertiesin the polymer blend.

The modified polypropylene (co)polymers and blends may be used in a widevariety of applications including thermoforming, blow moulding, tube orpipe extrusion, blown films, foams and extrusion coating.

The present invention may also be used in the recycling of wastepolypropylene or materials containing waste polypropylene.

The increased melt strength of the modified polypropylene (co)polymersrenders these (co)polymers more suitable for use in thermoformingapplications. The modified polypropylene (co)polymers may be used tothermoform containers such as margarine tubs. The benefits of thisinvention include that the polypropylene (co)polymers and blendscontaining same provide a wider temperature processing window thanconventional isotactic polypropylene. The modified polypropylene(co)polymers may also be used in large part thermoforming such as in theproduction of refrigerator liners and the like where conventionalisotactic polypropylene is unsuitable.

The modified polypropylene (co)polymers produced in accordance with thepresent invention are suitable for blow moulding and we have found thatthey can be more readily blow moulded into containers. Furthermore, theincreased melt strength makes it possible to produce large blow mouldedparts through the use of the high melt strength modified polypropylene(co)polymer. Thus components currently made by rotational moulding maynow be produced by blow moulding using the modified polypropylene(co)polymer of the present invention.

Profile extrusion for example tube or pipe extrusion, using the modifiedpolypropylene (co)polymer has been found to produce a more consistentproduct than conventional isotactic polypropylene.

Blown films made of polypropylene are generally blown downwards usingrelatively expensive equipment. The modified polypropylene (co)polymersof the present invention have sufficient melt strength for them to beable them to be blown upwardly using conventional polyethylene type filmblowing equipment which is less expensive and generally more convenientto operate. Advantageously the modified polypropylene (co)polymers ofthe present invention may be used in the production of blown films.

The modified polypropylene (co)polymers of the present invention mayalso be foamed with a wider processing window than for conventionalpolypropylene. Either a physical or chemical blowing agent may be used.It is preferred to use carbon dioxide as a physical blowing agent toproduce foams having a fine closed cell structure. Foamed pellets may besubsequently moulded to form components for use in a variety ofapplications such as automotive door trims, rooflinings, dash boards,bumpers and the like. Applications such as in foamed packaging are alsopossible, including thermoformed containers, insulating cups and thelike.

Waste polypropylene or waste steams containing a significant proportionof polypropylene are presently difficult to recycle as conventionally ahigh degree of chain scission results from the recycling process. Theprocess of the present invention may be used to upgrade recycled streamscontaining polypropylene by increasing the overall mechanical propertiesof the recycled polypropylene by the addition of initiator and monomerin accordance with the present invention.

The present invention will now be described with reference to thefollowing non-limiting examples. Described hereunder are the measurementtechniques used in the examples and a full description of the processconditions employed. Comparative Examples are labelled CE-n.

Melt Strength Measurement

Melt steps were measured on a “Rheotens” Melt Strength Tester, Type010.1, supplied by Gottfert Werkstoff-Prufmaschinen Gmbh of Buchen,Germany. This test involves drawing an extruded strand of polymervertically into the nip between two counter-rotating nip rollers. Thestrand was extruded using a Brabender Plasticord single screw extruderof screw diameter 19 mm and length to diameter ratio (L/D) of 25. Theextrudate exited via a right angle capillary die (2 mm diameter). Thetemperature profile used was uniform along the length of the barrel ofthe extruder and the die and was set at 190° C. The nip rollers aremounted on a balance arm which allows the force in the drawing strand tobe measured. The velocity of the nip rolls is increased at a uniformacceleration rate. As the test proceeds, the force increases untileventually the strand breaks. The force at breakage is termed the “meltstrength”.

While there is no internationally-established standard set of testrequirements for melt strength testing, comparative melt strength valuesobtained under the given set of test conditions provide a quantitativedetermination of the increase in melt strength used in the patent. Thetest conditions used were: die temperature 190° C., extruder output rate˜4 g/min, acceleration rate 1.2 cm/sec², draw distance 210 mm, mattfinish steel rollers.

Dow Rheology Index

The Dow Rheology Index (DRI) is believed in the art to be a measure ofthe long chain branching in a polymer. It is expressed as the deviationof a viscosity parameter obtained from shear rheology measurements on a“branched” polymer compared with that for a linear polymer. The branchedpolymers have lower values of the viscosity parameter than the linearpolymers (for a given relaxation parameter). The parameters are obtainedby fitting the Cross model to the shear viscosity flow curves. The DRImethod has been described by Lai, Plumley, Butler, Knight and Kao in apaper in SPE ANTEC '94 Conference Proceedings (pp1814-1818)—“DowRheology Index (DRI) for Insite Technology Polyolefins (ITP): UniqueStructure-Processing Relationships”.

Dynamic Rheology Tests

The dynamic rheology tests were performed on a Rheometrics DynamicStress Rheometer SR200. Test conditions were: parallel plates,temperature 190° C., frequency range 0.01 to 100 rad/sec, and 3-4%strain, in a nitrogen atmosphere to prevent degradation. G′ is thestorage modulus representing the elasticity of the polymer melt, G″ isthe loss modulus which represents the viscous component of thedeformation. The polydispersity index is 10 to power 5 divided by thecrossover modulus, which is the value of G′=G″ when the G′ and G″ curvescrossover—it is believed to be a measure of MWD. The higher G′, thegreater elasticity in the polymer and the higher the MW.

MFI

Melt flow indexes (MFI) were measured a 230° C. with a 2.16 kg loadaccording to ASTM 1238.

Drop Times

The drop times were determined by measuring the time taken for thepolypropylene strand (cut at the die face) to drop from the die of theextruder to the floor. The die of the JSW twin screw extruder was 1140mm above the floor. The drop time test combines the effects of meltviscosity, extensional viscosity, chain entanglement (as shown by dieswell), and elasticity (as shown by the tendency resist neck formation).Higher melt viscosity polypropylene polymers had drop times whichincorporated some additional effect due to prolonged cooling of theslower moving (falling) molten strand.

GPC

GPC molecular weights were determined using a Waters 150C hightemperature GPC unit. 1,2,4-trichlorobenzene was used as the solvent,eluting through two Styragel HT6E linear columns. The oven temperaturewas set at 140° C. and the pump flow rate was 1.0 ml/min.

Calibration was performed using narrow polydispersity polystyrenestandards. All molecular weights quoted as polystyrene equivalents.

-   -   Mn=number average molecular weight    -   Mw=weight average molecular weight    -   Mz=viscosity average molecular weight    -   Mp=peak molecular weight

Twin Screw Extruder

The twin screw extruder used in the examples was a JSW TEX-30 with a 30mm screw diameter and an overall L/D of 42. The extruder was operated ineither co-rotating (intermeshing self wiping) or counter rotating(intermeshing non-self wiping) modes with a throughput rate of between 5and 20 kg/hr and screw speeds of between 100 and 400 rpm as specified inTable 1. The melt temperature and pressures were monitored at threepoints along the barrel and in the die.

TABLE 1 Operating conditions Screw Feed Condi- Speed Rate TemperatureProfile tions (rpm) (kg/hr) (° C.) A 265 20 150° C., 175° C. (by 10) B265 20 180° C., 200° C. (by 3), 220° C. (by 7) C 150 5 120° C., 130° C.(by 4), 180° C. (by 6) D 265 20 140° C., 150° C. (by 10) E 265 20 180°C., 20D° C. (by 4), 230° C., 240° C., 250° C., 260° C., 270° C., 280° C.F 400 20 180° C., 220° C. (by 10) G 265 20 80° C., 120° C., 140° C.,160° C., 170° C., 180° C., 200° C. (by 5) H 150 5 80° C., 120° C., 140°C., 160° C., 170° C., 180° C., 190° C. (by 3), 200° C. (by 2) I 265 2080° C., 120° C., 140° C., 160° C., 170° C., 180° C., 190° C. (by 3),200° C. (by 2) J 250 20 150° C., 170° C. (by 3), 180° C., 200° C., 220°C. (by 5)

The temperatures in the table refer to sections of the barrel of theextruder that are capable of independent temperature control. The firstten temperatures are barrel section temperatures and the lasttemperature indicates the temperature of the die.

TABLE 2 Die configuration Condition Die Description 1 Large 3 holestrand die - 6 mm holes 2 Small 3 hole strand die - 4 mm holes 3 Large 2hole strand die - 6 mm holes 4 Single hole Brabender die - 10 mm hole

TABLE 3 Means of modifier addition Condition Die Description α Modifieradded at block 4 in 2-butanone carrier solvent β Modifier added at block4 in xylene carrier solvent γ Modifier coated onto PP powder - pretumble blended δ Modifier coated onto PP powder masterbatch

The overall extruder configuration and modifier conditions may berecited, for example, as condition: A1δ.

Solvent Addition of Modifiers

The initiator, and monomer if present, was introduced as a solution in2-butanone or xylene. The concentration of the initiator varied from5.6% wt/wt. The benzoyl peroxide and the di-toluol peroxides were bothpowders wetted with 25% (wt/wt) water. The monomer was present in anamount between 4 to 10% wt/wt solvent.

Increased levels of initiator were generally added by increasing thamount of solution added to the polymer melt. The additional peroxides(if any) were added with the initiator in the carrier solvent.

Solventless Addition of Modifiers

t-Butyl peroxybenzoate is a liquid. The solventless modification of thepolymer was achieved by absorbing the initiator onto powdered polymer orblending it with powdered polymer at concentrations ranging from 5%wt/wt to 10% wt/wt to form a masterbatch. The masterbatch was added tothe extruder in varying feed rates to alter the amount of additives. Theamount of polymer feed was adjusted accordingly to give constant overallfeed rate.

The stabilisers were also added as a masterbatch. The amount ofstabiliser was generally kept constant at 0.33% wt/wt Irganox 1010 and0.17% wt/wt Irgaphos 168 in the total composition.

The main polymer feed was added as either powder or pellets.

Single Screw Extruders Killion

The Killion single screw extruder used in the examples was a segmentedsingle screw extruder of L/D=40 (11 barrel sections, 10 heated) andscrew diameter of 31.75 mm.

Polypropylene powder, stabilisers (0.33% wt/wt Irganox 1010, 0.17% wt/wtIrgaphos 168 in total) and initiator were added to the feed throat ofthe single screw extruder via a twin screw K-Tron volumetric feeder.

Alternatively, the polypropylene powder and stabilisers were added viathe K-Tron feeder and polypropylene powder, stabilisers and themodifiers were added as a master batch via a single screw APV Accuratevolumetric feeder. The masterbatch contained 7.5% wt/wt benzoyl peroxide(prepared using a dispersion of benzoyl peroxide containing 25% wt/wtwater).

The output of the extruder was ˜1.5 kg/hr using a screw speed of 30 rpm.The set barrel temperature was either (I) a flat 220° C. with eachbarrel section and the die set at a temperature of 220° C. or (ii) 230°C./190° C. with the first six melting sections of the barrel set at 230°C. and the next four metering sections of the barrel and the die set at190° C. The melt temperature varied from 220 to 260° C.

Brabender

The Brabender single screw extruder used was a single screw extruder ofL/D=25 (4 Barrel sections), compression ratio 2.5:1 and screw diameterof 19 mm. The die was a 4 mm rod die.

The screw speed of the extruder was 20 rpm. The set barrel temperaturewas 140° C., 170° C., 180° C., 180° C. Residences time: Start 3 min 40sec; Middle 4 min 35 sec; and End 7 min 30 sec.

Polypropylene powder either as cryoground pellets or ex-reactor powderwas mixed with the modifiers and added to the feed throat, either floodfeed or by a Brabender single screw volumetric feeder.

The following commercial polypropylene (co)polymers were used in theexamples. The properties of the (co)polymers are shown in Table 4 below.

TABLE 4 Comparative data for a grade of high melt strength PP andconventional PP grades. MFI Melt Polymer 2.16 kg Strength ExamplePolymer Description @ 230° C. cN Control 1 Montell High melt strength 318 PF814 polypropylene homopolymer Control 2 Montell Extrusion grade 3 3JE6100 polypropylene homopolymer Control 3 ICI Injection moulding 14 1.8Australia grade of GYM 45 polypropylene homopolymer Control 4 ICIExtrusion grade of 4 2.8 Australia polypropylene GWM 22 homopolymerControl 5 ICI Thermoforming 0.8 6 Australia grade of PXCA 6152polypropylene homopolymer Control 6 ICI Injection moulding 14 1.4Australia grade of LYM 120 propylene/ethylene copolymer Control 7Montell Ex-reactor grade of 4.1 ˜3 6501 injection moulding polypropylenehomopolymer Control 8 Montell Extrusion grade of ˜3.5 — KM6100polypropylene homopolymer Control 9 Montell Extrusion grade of ˜3.5 —KMT6100 polypropylene homopolymer Control 10 Montell Ex-reactor grade of˜3.5 — KM6100 polypropylene powder homo- polymer- unstabalized *Meltstrength and MFI were measured for a particular batch and we have foundactual values vary up to 20% of these values.

EXAMPLES 1 TO 5

GYM45 was modified in accordance with Table 5 below. GYM45 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenehomopolymer.

TABLE 5 Motor Die Drop MFI Melt BPO Styrene Current Temp. Time 2.16 kg @Strength Example Conditions (wt %) (wt %) (amps) (° C.) (secs.) 230° C.(cN) Control 3 — — 0 — — — 14 1.8 CE 1 B1α 0 0 13 231 8 12.2 1.5 1 B1α0.36 0 13 229 9.7 14.4 1.9 2 B1α 0.7 0 13 229 13.5 14.4 2.3 3 B1α 0.95 013 230 17.1 12.5 3 4 D3α 1.0 0 19 197 23 9.7 4 5 D4α 0.34 0.45 21 17922.9 9.1 6.9

EXAMPLES 6 TO 18

GWM22 was modified in accordance with Table 6. GWM22 is an intermediatemolecular weight/medium MFI extrusion grade of polypropylenehomopolymer.

TABLE 6 Motor Die Drop MFI Melt BPO Styrene Current Temp. Time 2.16 kg @Strength Example Conditions (wt %) (wt %) (amps) (° C.) (secs.) 230° C.(cN) Control 4 4.5 2.8 CE 2 B1α 0 0 16 239 11.3 5 — 6 B1α 0.36 0 16 23415.2 6.3 3 7 B1α 0.75 0 17 238 21.8 5.9 4.7 8 B1α 1 0 16 239 25.4 5 6.99 B1α 1.3 0 20 236 25.3 5.6 7.1 10 B1α 0.12 0.16 16 237 8.0 4.15 — 11B1α 0.23 0.31 17 237 11.2 2.8 5 12 B1α 0.46 0.61 21 238 14 1.11 — 13 B1α0.69 0.92 21 241 14.2 0.69 18.6 14 B1α 1.22 1.63 21 248 — — 18.6 15 E1α0.33 0.44 17 281 20 3.6 8.2 16 C2α 0.81 4.2 18 203 60 0.69 18.8 17 E1α0.31 0.40 20 275 23 3.1 7.0 18 E1α 0.30 0.53 17 277 24 3.4 9.1

The increase in complex viscosity of example 14, 16, 17 and 18 is shownin FIG. 1. G′ has been plotted against frequency in FIG. 2.

The modified polypropylene's of examples 14, 16, 17 and 18 were testedfor additional physical properties and it was found that the modifiedpolypropylene's had:

14 16 17 18 Control 4 i) Elasticity 1200 680 40 45 10 G′ @ 0.01 rad/s(pa) rad/s (Pa) ii) 1/Relaxation ˜0.0013 0.085 15 18 23 Crossover TimeFrequency (rad/sec) iii) Polydispersity 222 39 4.4 4.7 3.7 M_(w)/M_(n)Index iv) Dow 192 86 2.0 5.6 0 LongChain Rheology Branching Index

EXAMPLES 19 TO 26

PXCA6152 was modified in accordance with Table 7 below. PXCA6152 is ahigh molecular weight/low MFI thermoforming grade of polypropylenehomopolymer.

TABLE 7 Motor Die Drop MFI Melt BPO Styrene Current Temp. Time 2.16 kg @Strength Example Conditions (wt %) (wt %) (amps) (° C.) (secs.) 230° C.(cN) Control 5 0.8 6 CE 3 F1α 0 0 17 251 14.6 1.1 — 19 B1α 0.34 0 22 24425.9 1.3 7.4 20 B1α 0.68 0 23 250 22.8 1.1 11.1 21 B1α 0.8 0 24 246 30.50.8 14 22 B1α 1.04 0 24 247 25.3 0.65 17.7 23 F1α 0.31 0.41 21 256 24.40.42 17.5 24 F1α 0.47 0.63 21 264 25 0.31 — 25 F1α 0.55 0.73 23 269 —0.40 — 26 F1α 0.71 0.95 22 259 25 0.35 21.3

The modified polypropylene of example 22 was tested for additionalphysical properties and it was found that the modified polypropylenehad:

i) Elasticity 200 G′ @ 0.01 rad/s (Pa) ii) 1/Relaxation Time 7.1Crossover frequency (rad/sec) iii) Polydispersity Index 3.9 M_(w)/M_(n)iv) Dow Rheology Index 10 Long Chain Branching

The DRI of the base polypropylene material, PXCA 6152 (an unbranchedpolypropylene) was expected to be 0. The DRI of the modifiedpolypropylene demonstrates a significant degree of long chain branching.

EXAMPLES 27 TO 33

LYM120 was modified in accordance with Table 8 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of PP copolymer.

TABLE 8 Motor Die Drop MFI Melt BPO Styrene Current Temp. Time 2.16 kg @Strength Example Conditions (wt %) (wt %) (amps) (° C.) (secs.) 230° C.(cN) Control 6 12.2 1.4 27 D2α 0.68 0 13 182 19.3 13.1 2.3 28 A4α 1.08 019.5 200 31 9 4.2 29 A2α 0.33 0.44 18 202 28 5.8 7.4 30 D2α 0.32 0.42 23185 46.5 3.8 9.0 31 A4α 0.42 0.55 19.5 204 31.1 6.5 11.2 32 A4α 0.620.83 20 201 36.8 — 11.9 33 A4β 0.34 0.45 16 199 25.1 — 4.3

EXAMPLES 34 TO 42

Ex-reactor GYM45 powder was modified according to Table 9 below. GYM45is a low molecular weight/higher MFI injection moulding grade ofpolypropylene homopolymer. The polypropylene was stabilized with Irganox1010 (0.33 wt %) and Irgaphos (0.17 wt %). The modifiers and stabilizerswere added to the twin-screw extruder at the feed throat.

TABLE 9 Motor Die Drop MFI Melt BPO Styrene Current Temp. Time 2.16 kg @Strength Example Conditions (wt %) (wt %) (amps) (° C.) (secs.) 230° C.(cN) Control 3 — — — — — — 14 1.8 CE 4 H3δ 0 0 7 209 21.5 11.3 1.7 34I3δ 0.38 0 14 209 12.1 13.6 1.9 36 I3δ 0.75 0 15 210 15.0 11.8 2.6 37I3δ 1.5 0 15 214 20.6 10.3 5.7 38 H3δ 0.75 0 6 209 35.5 17.6 2.1 39 H3δ1.13 0 8 208 39.5 13.3 2.9 40 H3δ 1.5 0 8 208 43.3 9.8 4.4 41 I3δ 0.150.2 18 215 16.6 9.6 2.0 42 I3δ 0.23 0.3 16 214 20.5 6.5 5.5

EXAMPLES 43 TO 49

GYM45 was modified in accordance with Table 10 below. GYM45 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenehomopolymer.

TABLE 10 Motor Die Drop MFI Initiator Styrene Current Temp. Time 2.16 kg@ Example Conditions Initiator (wt %) (wt %) (amps) (° C.) (secs) 230°C. CE 5 A3α — 0 0 18 192 11.8 12.8 43 A3α BPO 0.12 0.16 16 197 14 14.444 A3α BPO 0.21 0.28 17 200 18.8 9.8 45 A3α BPO 0.41 0.55 20 206 27.65.6 46 A3α BPO 0.62 0.83 22 208 32.2 3.6 CE-6 A3α DHBP 0.33 0.09 14.5191 4.6 55. CE-7 A3α DHBP 0.60 0.17 16 190 4 117 CE-8 A3α DHBP 0.90 0.2814.5 190 3.9 132 CE-9 A3α TBEH 0.33 0.34 16 191 9.9 18.3 CE-10 A3α TBEH0.60 0.62 17 192 10 19.5 CE-11 A3α TBEH 0.90 0.93 17 193 10.6 17.2 47A3α TBPB 0.30 0.30 15 194 7.8 58.3 48 A3α TBPB 0.68 0.70 17 198 14 47.349 A3α TBPB 0.89 0.91 19 199 15.6 38.5 CE-12 A3α DCP 0.08 0.09 14.5 1924.3 48.5 CE-13 A3α DCP 0.17 0.17 15 191 3.9 64.7 CE-14 A3α DCP 0.25 0.2515 191 3.7 90.3 CE-15 A3α DLP 0.33 0.33 15 190 11.2 16.5 CE-16 A3α DLP0.63 0.64 15 190 11.1 15.1 CE-17 A3α DLP 0.92 0.93 15 190 11.1 18.0

EXAMPLES 50 TO 54

LYM120 was modified in accordance with Table 11 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 11 Motor Die Drop MFI Melt BPO Current Temp Time 2.16 kg @Strength Example Conditions (wt %) (amps) (° C.) (secs.) 230° C. (cN)Control 6 12.2 1.4 CE 18 H3δ 0 7 209 18.4 11.3 1.2 52 H3δ 0.75 8 21050.5 6.9 2.6 53 H3δ 1.13 8 210 47.0 6.6 3.3 54 I3δ 1.5 14 217 18.5 3.86.1

EXAMPLES 55 TO 61

LYM120 was modified in accordance with Table 12 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 12 Motor Die Drop MFI Melt Initiator Styrene Current Temp. Time2.16 kg @ Strength Example Conditions Initiator (wt %) (wt %) (amps) (°C.) (secs) 230° C. (cN) CE-19 A3α BPO 0.00 0.00 16 195 9.9 12.8 1.1 55A3α BPO 0.12 0.16 15 197 13.9 10.9 56 A3α BPO 0.21 0.28 17.5 201 17.77.50 57 A3α BPO 0.41 0.55 20 208 25.8 4.4 11.5 58 A3α BPO 0.62 0.83 21209 26.5 2.9 CE-20 A3α DHBP 0.08 0.09 13.5 191 4.9 52 CE-21 A3α DHBP0.16 0.17 14 190 5.3 79 CE-22 A3α DHBP 0.28 0.30 14.5 190 5.6 114 CE-23A3α TBEH 0.31 0.32 14 192 8.6 17.8 CE-24 A3α TBEH 0.62 0.64 14 192 917.4 CE-25 A3α TBEH 0.98 1.01 14 192 9.6 15.4 59 A3α TBPB 0.30 0.31 14196 4.6 33.8 60 A3α TBPB 0.61 0.62 17 200 14.6 32.9 61 A3α TBPB 0.930.95 17 202 15.6 23.1 CE-26 A3α DCP 0.08 0.09 13 192 5 38.6 CE-27 A3αDCP 0.17 0.17 13.5 190 5.5 57.6 CE-28 A3α DCP 0.27 0.28 14 190 6.2 65.9CE-29 A3α DLP 0.31 0.31 15 191 9.9 15.7 CE-30 A3α DLP 0.64 0.65 13.5 1909.8 14.8 CE-31 A3α DLP 1.00 1.01 13 190 14.8

EXAMPLES 62 TO 73

LYM120 was modified in accordance with Table 13 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 13 Motor Die Drop MFI Melt Initiator Styrene Current Temp. Time2.16 kg @ Strength Example Conditions Initiator (wt %) (wt %) (amps) (°C.) (secs) 230° C. (cN) CE-32 A3δ — 0 14.5 200 10 12.4 1.1 62 A3δ BPO0.11 0 14 199 10 11.5 1.1 63 A3δ BPO 0.23 0 16.5 201 15.1 9.0 1.2 64 A3δBPO 0.45 0 16.5 203 20.6 6.6 1.7 65 A3δ BPO 0.68 0 17.5 206 20.6 5.4 4.166 A3δ BPO 1.13 0 18 206 18.6 5.7 3.9 CE-33 A3δ DLP 0.31 0 13.5 198 9.313.6 — CE-34 A3δ DLP 0.59 0 14 199 8.8 14.4 — CE-35 A3δ DLP 0.89 0 13196 8.9 15.0 — CE-36 A3δ TBPB 0.07 0 12 189 5.1 28.7 — CE-37 A3δ TBPB0.15 0 12 190 5.3 31.0 — CE-38 A3δ TBPB 0.29 0 10.5 185 6.3 92.0 0.5CE-39 A3δ TBPB 0.59 0 11 186 11.2 102.0 — 67 A3δ BPO 0.11 0.15 17.5 20519.1 5.7 2.4 68 A3δ BPO 0.23 0.30 19.5 210 25 4.3 6.3 69 A3δ BPO 0.450.6 21.5 209 27.8 2.1 10.4 70 A3δ BPO 0.90 1.2 23.5 210 26.8 1.3 12.2CE-40 A3δ DLP 0.30 0.3 14.5 199 9.4 14.1 — CE-41 A3δ DLP 0.59 0.6 13 1979.3 17.2 — CE-42 A3δ DLP 0.89 0.9 13 197 9.8 16.1 — 71 A3δ TBPB 0.29 0.313.5 196 11.4 20.4 3.7 72 A3δ TBPB 0.59 0.6 16.5 200 20.2 12.9 — 73 A3δTBPB 1.18 1.2 17 202 18.8 13.9 4.5

EXAMPLES 74 TO 77

GYM45 was modified in accordance with Table 13 below. GYM45 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenehomopolymer.

TABLE 13 Motor Die Drop MFI Initiator Current Temp. Time 2.16 kg @Example Conditions Initiator (wt %) (amps) (° C.) (secs) 230° C. CE 43A3α — 0 18 192 11.8 12.8 74 A3α BPO 0.23 16.5 196 10.35 17.0 75 A3α BPO0.45 17 199 11.8 17.3 76 A3α BPO 0.73 17 200 15.9 15.4 77 A3α BPO 0.9618 202 17.3 14.9 CE-44 A3α DHBP 0.08 15 191 3.6 96 CE-45 A3α DHBP 0.1714.5 190 3.1 169 CE-46 A3α DHBP 0.29 13 188 2.3 >100 CE-47 A3α DHBP 0.3013 188 2.2 >200 CE-48 A3α DHBP 0.50 13.5 186 1.9 >200 CE-49 A3α DHBP0.57 12 186 1.9 >100 CE-50 A3α TBEH 0.30 17 197 8.8 12.0 CE-51 A3α TBEH0.64 14 188 7.2 24.4 CE-52 A3α TBEH 0.98 14 189 6.8 25.6 CE-53 A3α TBPB0.31 13 186 2.6 95 CE-54 A3α TBPB 0.64 13 184 2.1 238 CE-55 A3α TBPB1.03 12 184 1.9 >250 CE-56 A3α DCP 0.08 16 192 3.8 47.1 CE-57 A3α DCP0.17 14 189 2.9 121.3 CE-58 A3α DLP 0.32 16 191 10.9 14.5 CE-59 A3α DLP0.64 16 190 10.6 17.9 CE-60 A3α DLP 0.95 16 189 10.4 16.6

EXAMPLES 78 TO 82

LYM120 was modified in accordance with Table 14 below. LYM120 is a lowmolecular weigh/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 14 Motor Die Drop MFI Initiator Current Temp. Time 2.16 kg @Example Conditions Initiator (wt %) (amps) (° C.) (secs) 230° C. Control24 A3α BPO 0 16 195 9.9 12.8 78 A3α BPO 0.25 15 196 10.3 13.4 79 A3α BPO0.47 14 198 13.2 13.1 80 A3α BPO 0.64 16 198 13.9 12.9 81 A3α BPO 0.7017 201 13.6 11.9 82 A3α BPO 0.94 18 198 13.5 10.6 CE-61 A3α DHBP 0.09 14190 3.6 80 CE-62 A3α DHBP 0.16 13 188 3.1 160 CE-63 A3α DHBP 0.26 13 1872.8 250 CE-64 A3α TBEH 0.29 15 193 7 CE-65 A3α TBEH 0.60 13 192 6.7 19.4CE-66 A3α TBEH 1.02 12 191 6 22.6 CE-67 A3α TBPB 0.30 13 186 3.6 85CE-68 A3α TBPB 0.61 12 184 3.8 173 CE-69 A3α TBPB 0.92 12 184 3.4 >250CE-70 A3α DCP 0.08 16 192 4.5 14.6 CE-71 A3α DCP 0.17 13 190 3 107 CE-72A3α DCP 0.25 13 188 3 131 CE-73 A3α DLP 0.32 14.5 191 9.5 14.3 CE-74 A3αDLP 0.68 15 191 9.4 15.8 CE-75 A3α DLP 0.98 14.5 193 8.7 21.0

EXAMPLES 83 TO 92

LYM120 was modified in accordance with Table 15 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 15 Mole Motor Die Drop MFI Melt Initiator Styrene Ratio CurrentTemp. Time 2.16 kg @ Strength Example Conditions Initiator (wt %) (wt %)Sty/Init (amps) (° C.) (secs) 230° C. (cN) CE-76 A3α 0 0 0 — 16 195 9.912.8 1.1 83 A3α BPO 0.43 0.19 1.04 16 207 18.5 6.9 — 84 A3α BPO 0.410.37 2.07 19 207 22.5 4.9 — 85 A3α BPO 0.41 0.55 3.11 20 208 25.8 4.411.6 86 A3α BPO 0.43 0.76 4.14 21 210 25.4 3.9 — 87 A3α BPO 0.45 0.995.18 20 205 28.3 4.4 — 88 A3α TBPB 0.56 0.19 0.78 13 192 8.9 71 — 89 A3αTBPB 0.55 0.37 1.57 14 196 11.0 38 — 90 A3α TBPB 0.61 0.62 1.91 17 20014.6 33 — 91 A3α TBPB 0.54 0.73 3.14 16 201 16.0 19.2 — 92 A3α TBPB 0.580.97 3.92 19 204 16.2 15.7 — CE-77 A3α DHBP 0.27 0.1 0.84 13 190 4.4 187— CE-78 A3α DHBP 0.25 0.18 1.69 14 191 5.3 125 — CE-79 A3α DHBP 0.280.30 3.04 14.5 190 5.6 114 — CE-80 A3α DHBP 0.27 0.40 3.38 15 193 6.2116 — CE-81 A3α DHBP 0.28 0.50 4.22 14 192 6.1 118 —

EXAMPLES 93 TO 97

GYM45 was modified in accordance with Table 16 below. GYM45 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenehomopolymer.

TABLE 16 Mole Motor Die Drop MFI Initiator Styrene Ratio Current TempTime 2.16 kg @ Example Conditions Initiator (wt %) (wt %) Sty/Init(amps) (° C.) (secs) 230° C. CE-82 A3α — 0.00 0.00 0.00 18 192 11.812.75 93 A3α BPO 0.36 0.16 1.04 18 202 18.1 11.17 94 A3α BPO 0.41 0.372.07 18 209 23.5 6.38 95 A3α BPO 0.41 0.55 3.11 20 206 27.6 5.62 96 A3αBPO 0.43 0.76 4.14 22 209 25.7 4.05 97 A3α BPO 0.40 0.89 5.18 21 20731.2 4.27

EXAMPLE 98 TO 105

LYM120 was modified in accordance with Table 17 below. LYM120 is a lowmolecular weight/higher MFI injection moulding grade of polypropylenecopolymer.

TABLE 17 Mole ratio Motor Drop Die Melt Initiator Initiator Mole ratioMonomer Monomer/ Current time Temp strength Example Conditions #1 wt %#2 wt % Init #1/Init #2 wt % tot init (amps) secs ° C. MFI (cN)Initiator #1 = BPO, Initiator #2 = DHBP, Monomer = Styrene 98 A3δ 0.430.06 9.08 0.57 2.81 19 17 204 6.9 3.8 99 A3δ 0.43 0.11 4.54 0.58 2.57 1914.8 203 10.5 2.9 100 A3δ 0.43 0.17 3.03 0.58 2.37 18 14 201 16.9 —Initiator #1 = BPO, Initiator #2 = TBPB, Monomer = Styrene 101 A3δ 0.430.11 3.07 0.58 2.36 20 18.7 208 5 5.5 102 A3δ 0.43 0.22 1.53 0.58 1.9217 14.2 204 9.3 4.2 103 A3δ 0.43 0.34 1.02 0.59 1.62 18 14 204 11.6 —104 A3δ 0.43 0.45 0.77 0.60 1.40 18 11.8 201 19.5 — 105 A3δ 0.43 0.341.02 0.94 2.59 21 17 207 7.5 6.3

EXAMPLE 108 TO 109

Montell 6501 was modified in accordance with Table 19 below on theKillion screw extruder described above.

Barrel Extruder Motor Die Drop Temp Output BPO Styrene Current Temp TimeMFI Sample (° C.) (kg/hr) wt % wt % (amps) (° C.) (secs) (g/10 min)Control 7 — — — — — — — 4.1 CE 84 220 1.4 0 0 6 256 17 4.1 flat 108 2201.4 2.1 0.25 6 260 35 2.2 flat 109 220 1.4 4.2 0.5 7.5 263 33 0.40 flat

EXAMPLES 40, 41, 7, 12, 28, 29, 31 AND 14

GPC molecular weights were determined using a Waters 150C hightemperature GPC unit. 1,2,4-trichlorobenzene was used as the solvent,eluting through two Ultrastyragel linear columns. The oven temperaturewas set at 140° C. and the pump flow rate was 1.0 ml/min.

Calibration was performed using narrow polydispersity polystyrenestandards. All molecular weights quoted as linear polystyreneequivalents.

-   -   Mn=number average molecular weight    -   Mw=weight average molecular weight    -   Mz=viscosity average molecular weight    -   Mp=peak molecular weight

Error are quoted as two times the standard deviation between duplicateinjections.

TABLE 20 Melt Example BPO Sty MFI str Mn Mw Mz Mp No. Cond. (wt %) (wt%) (g/10 min) (cN) (g/mol) × 10⁻³ (g/mol) × 10⁻³ (g/mol) × 10⁻³ (g/mol)× 10⁻³ Intermediate Molecular Weight PP Homopolymer (GWM 22) Control 4 —— — 4.5 2.8 55 295 1200 105 8 B1α 1.0 5.0 6.9 80 425 1415 200 10 B1α0.12 0.16 4.15 — 90 405 1200 235 11 B1α 0.23 0.31 2.80 5.0 75 415 1400195 12 B1α 0.46 0.61 1.11 — 70 555 2200 205 13 B1α 0.69 0.92 0.69 18.685 575 2200 180 110 C2α 1.50 3.8 — 75 430 1560 160 111 C2α 2.23 3.2 — 75430 1700 150 112 C1α 0.37 0.49 2.22 — 85 565 2035 215 113 C1α 0.60 0.801.00 19.4 85 690 2575 170 114 C1α 0.32 1.65 4.50 — 80 505 1835 170 115C1α 0.47 2.45 1.58 — 90 605 2160 205 116 C1α 0.81 4.19 0.69 18.8 85 6752610 185 Low Molecular Weight PP Copolymer (PXCA 6152) Control 5 — — —12.4 1.4 45 230 720 130 22 B1α 1.04 0.65 17.7 110 485 1615 195 27 A2α0.33 0.44 — 7.4 65 325 1045 140 61 A2α 0.41 0.55 4.4 11.5 60 325 1315125 62 A2α 0.62 0.83 2.9 — 70 460 2435 135 — D2α 0.28 0.38 — — 80 5552875 160 28 D2α 0.32 0.44 — 9.0 120 640 4130 140 78 A3α 0.25 13.4 — 70315 1330 135 79 A3α 0.47 13.1 — 65 320 1380 130 80 A3α 0.64 12.9 — 65360 1975 130 27 D3α 0.68 13.1 2.3 70 445 1865 140 *Errors in themolecular weight are generally less than 30% of the quoted value, as isusual in high temperature GPC under the conditions employed.

EXAMPLES 110 TO 114

GWM22 and KM6100 were modified in accordance with Table 20 below.

Table 20: Effect of feed throat addition of BPO on the modification ofprestabilised PP homopolymer.

TABLE 20 Effect of feed throat addition of BPO on the modification ofprestabilised PP homopolymer Powder Motor Drop Die Melt wt % BPO CurrentTime Temp MFI Str. Example Conditions α (wt %) (amps) (sec) ° C. (g/10min.) (cN) Prestabilised PP homopolymer GWM 22 Control 4 ˜4 2.8 110 J3δ8.8 0.92 25 18 244 3.9 11.0 111 J3δ 13.3 1.40 30 19 248 2.6 8.5Prestabilised PP Homopolymer KM6100 Control 8 ˜3.5 2.5 CE-85 J3δ 0 0 2711 240 3.7 2.5 112 J3δ 2.0 0.41 26 15 235 4.9 3.9 113 J3δ 3.9 0.81 27 19241 3.3 6.7 114 J3δ 6.2 1.28 28 19 241 2.7 9.5 α: BPO added to pelletfeed in PP powder derived from cryoground prestabilised PP pellets

EXAMPLES 115 TO 117

KMT6100 was modified in accordance with Table 22 below. KMT6100 is aprestabilised PP copolymer.

Table 22: Effect of feed throat addition of BPO on the modification ofprestabilised PP homopolymer.

TABLE 22 Effect of feed throat addition of BPO on the modification ofprestabilised PP homopolymer Powder Motor Drop Die Melt wt % BPO CurrentTime Temp MFI Str. Example Conditions α (wt %) (amps) (sec) ° C. (g/10min.) (cN) Control 9 ˜3.5 2.0 CE-86 J3δ 0 0 24 8 231 4.4 2.0 115 J3δ 1.90.40 25 10 233 5.4 1.9 116 J3δ 3.0 0.81 24 13 235 4.4 3.1 117 J3δ 5.91.22 29 15 237 3.0 4.5 α: BPO added to pellet feed in PP powder derivedfrom cryoground prestabilised PP pellets

EXAMPLES 118 TO 121

KM6100u was modified with para-toluoyl peroxide (PTP) and BPO inaccordance with Table 23 below. The KM6100u was stabilized with Irganox1010 (0.33 wt %) and Irgaphos 168 (0.17 wt %) which were added to themain feed throat of the extruder.

TABLE 23 Motor Drop Die Melt Peroxide Current Time Temp MFI Str. ExampleConditions Peroxide (wt %) (amps) (sec) ° C. (g/10 min.) (cN) Control˜3.5 ˜2.5 10 CE-87 J3δ — 0 22 9 240 5.2 2.7 118 J3δ BPO 1.0 22 17 2525.2 7.2 119 J3δ PTP 1.0 21 16 240 5.2 6.8 120 J3δ PTP 1.5 22 18 239 3.914.2 121 J3δ PTP 2.0 24 243 3.4 14.0

EXAMPLES 122 TO 128

PXCA6152 was modified with mixed initiator systems in accordance withTable 24 below.

TABLE 24 Motor Drop Die Melt Init #1 Init #2 Mole ratio Current TimeTemp MFI Str. Example Conditions wt % wt % Init #1/Init #2 (amps) (sec)° C. (g/10 min.) (cN) Control 5 0.8 6 CE-88 B3α 0 0 — 22 14 255 0.9 5.1122 B3α 0.87 0 — 24 20 257 1.28 14.2 Initiator #1 = BPO, Initiator #2 =DHBP 123 B3α 0.87 0.045 23.2 22 19 251 4.0 8.0 124 B3α 0.87 0.064 16.320 16 250 5.4 — 125 B3α 0.87 0.084 12.4 20 15 248 6.4 0.2 Initiator #1 =BPO, Initiator #2 = TBPB 126 B3α 0.87 0.006 129.4 22 16 254 3.4 — 127B3α 0.87 0.012 64.7 20 16 249 3.9 0.5 128 B3α 0.87 0.019 40.9 20 16 2496.4 0.1

EXAMPLES 129 TO 132

Cryoground PXCA6152 in the form in the form of a powder was modifiedwith initiator system according to Table 25 below.

TABLE 25 Effect of Mixed Initiators on the Modification of PXCA6152Powder α (cryoground pellets) Motor Drop Die Melt Init #1 Init #2 Moleratio Current Time Temp MFI Str. Example Conditions wt % wt % Init#1/Init #2 (amps) (sec) ° C. (g/10 min.) (cN) Control 5 0.8 6 CE-89 B3δ0 0 — 25 13 256 1.0 — Initiator #1 = BPO, Initiator #2 = DHBP 129 B3δ0.86 0 — 23 17 253 1.8 10.8 130 B3δ 0.87 0.004 23 17 254 2.1 8.8Initiator #1 = BPO, Initiator #2 = TBPB 131 B3δ 0.87 0.016 24 18 253 2.68.2 132 B3δ 0.87 0.026 23 17 253 3.6 7.7

EXAMPLES 79 TO 85

LYM120 was modified in accordance with Table 26 below.

TABLE 26 Motor Drop Die Melt BPO Monomer/ Monomer Current Time Temp MFIStr. Example Conditions wt % Coagent wt % (amps) (sec) ° C. (g/10 min.)(cN) Control 6 12.2 1.4 CE-76 Aα 0 none 0 16 10 195 12.8 1.1 79 Aα 0.47none 0 14 13 198 13.2 — 85 Aα 0.41 Styrene 0.54 20 25.8 208 4.4 11.6

EXAMPLE 133

GYM 22 was modified in accordance with Table 27 below.

TABLE 27 Motor Drop Die Melt Conditions BPO Monomer/ Monomer CurrentTime Temp MFI Str. Example α wt % Coagent wt % (amps) (sec) ° C. (g/10min.) (cN) Control 4 4.5 2.8 CE-2 B1α 0 none — 16 11 239 5 — 6 B1α 0.36none — 16 15 234 6.3 3 133 B1α 0.34 Styrene 0.45 21 29 250 1.72 —

EXAMPLES 134 TO 137

Cryoground KM6100 in the form of a powder was modified on a Brabendersingle screw extruder in accordance with the general description of theBrabender SSE above and Table 28 below. The initiator was added at thefeed throat of the SSE along with the stabilizers (0.33 wt % Irganox1010 and 0.17 wt % Irgaphos 168).

TABLE 28 Peroxide Peroxide MFI Example Type (wt %) (g/10 min.) Control 8— 0 3.5 134 BPO 1 2.9 135 PTP 0.5 3.8 136 PTP 1 3.3 137 PTP 2 2.0 *PTP -Paratoluol Peroxide (bis paramethyl benzoyl peroxide)

EXAMPLE 138

PXCA6152 was modified in accordance with Table 29 below.

TABLE 29 Modification of PXCA6152 Pellets Motor Drop Die Melt BPOStyrene Current Time Temp MFI Str. Example Conditions wt % wt % (amps)(sec) ° C. (g/10 min.) (cN) Control 5 0.8 6.0 CE-94 B3α 0 — 22 14 2550.9 5.1 138 B3α 0.51 0.68 24 19 279 0.6 21.0

EXAMPLES 139 TO 143

The modified PXCA6152 produced according to Example 138 was melt withGYM45 in accordance with Table 30.

TABLE 30 Blends of the Modified PP with other PP Homopolymers Motor DropDie Current time Temp Melt Example Conditions PP#1 (wt %) PP#1 (wt %)(amps) (seconds) ° C. MFI Strength CE-95 A3 Control 5 (5) Control 3 (95)18 11 206 9.9 CE-96 A3 Control 5 (10) Control 3 (90) 19 12 202 7.8 CE-97A3 Control 5 (15) Control 3 (95) 19 13 202 7.0 CE-98 A3 Control 5 (20)Control 3 (80) 19 14 202 5.5 CE-99 A3 Control 5 (25) Control 3 (75) 1915 202 4.7 2.6 139 A3 138 (5) Control 3 (95) 19 15 199 9.3 140 A3 138(10) Control 3 (90) 19 16 201 7.4 141 A3 138 (15) Control 3 (85) 19 18203 6.6 142 A3 138 (20) Control 3 (80) 20 19 204 5.0 143 A3 138 (25)Control 3 (75) 19 20 207 4.7 5.2 CE-100 A3 — Control 4 (100) 20 15 2085.3 144 A3 138 (5) Control 4 (95) 21 18 207 3.7 145 A3 138 (10) Control4 (90) 21 19 206 3.5 146 A3 138 (15) Control 4 (85) 22 21 210 2.3 147 A3138 (20) Control 4 (80) 22 21 212 2.6 148 A3 138 (25) Control 4 (75) 2323 213 2.4 7.7

EXAMPLES OF CARBON DIOXIDE FOAMING OF MODIFIED PP

The equipment used for foaming the polypropylene (from earlier examples)was a tandem extrusion line made up of an Leitritz twin screw extruder(34 mm screw diameter, co-rotating, with 11 barrel sections) connectedvia a melt pipe to a single screw extruder (43 mm screw diameter). CO₂was introduced into barrel six of the twin screw extruder. The gassedpolymer was then cooled slowly in the single screw extruder.

MFI Melt Foaming Av Foam (g/10 Strength Temp Density Av Cell SizeExample min) (cN) (20 C.) (g/cc) (μm) Control 1 3 18 166 to 159 0.058550 25 0.4 — 169 to 159 0.044 300 31 6.5 11.2 167 to 161 0.051 280

Non high melt strength grades of polypropylene have foam temperatureprocessing windows of less than 1° C.

Foamed examples 13 and 17 both has a fine closed cell structure.

EXAMPLES OF THERMOFORMING

The modified polypropylene produced in Example 69 was extruded on aWelex single screw extruder through a sheet die to produce a sheet 78 cmwide and ^(˜)1.25 mm thick. The sheet was fed to a Gabler F702continuous thermoformer to produce margarine tubs. Tubs produced fromthe modified PP sample had a crush strength of 25 kg after 1 hour. Noappreciable sag was noticed of the PP sheet during the process.

Blow Moulding

The modified polypropylene of Example 5 was blow moulded on Bekum blowmoulder fitted with a general purpose polyolefin screw using a 750 mlscrew top bottle mould, (radially non symmetrical bottle with waist).The mould temperature was 0° C.

The blow mouldability of the modified injection moulding grade of PP wascompared against that of a commercial low melt flow index PP homopolymer(ICI GWM110 of MFI=1.5).

It was found that the modified PP homopolymer (MFI=9.1 and MeltStrength=6.9 cN) could be easily blow moulded into 750 ml bottles.Conventional PP of similar MFI could not be successfully blow moulded.The modified PP gave similar performance to an extrusion grade PP of lowMFI.

The results are very promising where a higher MFI PP could be used toblow bottles. This possibly opens up the opportunity to produce largeblow moulded parts through use of a high melt strength modified PP whichhas been tailored to have an MFI acceptable to blow moulding (ie 1-2MFI).

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications which fall within itsspirit and scope. The invention also includes all of the steps,features, compositions and compounds referred to or indicated in thisspecification, individually or collectively, and any and allcombinations of any two or more of said steps or features.

1. A process for increasing the melt strength and/or the extensionalmelt viscosity of a polypropylene (co)polymer, the process comprisingmelt mixing a polypropylene (co)polymer in the presence of an initiatorand optionally a monoene monomer wherein said initiator is selected fromthe group defined by formula 1:

wherein R is selected from the group consisting of optionallysubstituted C₁ to C₁₈ acyl, optionally substituted C₁ to C₁₈ alkyl,aroyl defined by formula 2,

and groups of formula 3,

wherein U, V, X, Y, Z, U′, V′, X′, Y′ and Z′ are independently selectedfrom the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl,aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4,

and wherein T is alkylene; wherein the melt strength and/or theextensional melt viscosity of the polypropylene (co)polymer is increasedduring the melt mixing step.
 2. The process according to claim 1 whereinthe initiator is selected from compounds of formula
 6.

where X, Y, Z, U, V, X′, Y′, Z′, U′, V′ are independently selected fromthe group consisting of hydrogen and C₁-C₁₈ alkyl where at least one ofX, Y, Z, U, V and X′, Y′, Z′, U′, V′ are not hydrogen.
 3. The processaccording to claim 2 wherein the initiator is selected from the groupconsisting of Dibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, M,M′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide,m,p′-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (allisomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl)peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers),Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide(all isomers), Bis(octylbenzoyl) peroxide (all isomers),Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide(all isomers), Bis(ethoxybenzoyl) peroxide (all isomers),Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide(all isomers), Bis(pentoxybenzoyl) peroxide (all isomers),Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl)peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers),Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide(all isomers), Bis(fluorobenzoyl) peroxide (all isomers),Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide(all isomers), Bis(trimethylbenzoyl) peroxide (all isomers),Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tertbutoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide (all isomers),Bis(2,6-dimethyl-4-trimethylsilyl benzoyl) peroxide and isomers,2,2′(dioxydicarbonyl) bis—Benzoic acid dibutyl ester where the term “allisomers” refers to any variation in the position of the ring substituentas well as the structure of the substituent itself.
 4. The processaccording to claim 1 wherein the initiator is selected from the groupconsisting of tert-butyl perbenzoate, tert-butyl (methyl)perbenzoate(all isomers), tert-butyl (ethyl)perbenzoate (all isomers), tert-butyl(octyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (allisomers), tert-amyl perbenzoate, tert-amyl (methyl)perbenzoate (allisomers), tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl(octyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (allisomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl(octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate(all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl(methyl)perbenzoate (all isomers), 2-ethylhexyl (ethyl)perbenzoate (allisomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl(nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (allisomers), 2-ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl(octyloxy)perbenzoate (all isomers), and 2-ethylhexyl(nonyloxy)perbenzoate (all isomers).
 5. The process according to claim 1wherein the initiator is selected from the group consisting of Bis(tertbutylmonoperoxy phthaloyl) diperoxy terephthalate, Bis(tertamylmonoperoxy phthaloyl) diperoxy terephthalate diacetyl phthaloyldiperoxide, dibenzoyl phthaloyl diperoxide, bis(4 methylbenzoyl)phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, dibenzoylterephthaloyl diperoxide, andPoly[dioxycarbonyldioxy(1,1,4,4-tetramethyl-1,4-butanediyl)] peroxide.6. The process according to claim 1 wherein the initiator has a 0.1 hourhalf life in the range 100-170° C.
 7. The process according to claim 1wherein the initiator is present in a range of from 0.004 to 0.25 molesof initiator per kg of the polypropylene homopolymer or copolymer. 8.The process according to claim 7 wherein the initiator is present in therange of from 0.006 to 0.10 moles of initiator per kg of thepolypropylene homopolymer or copolymer.
 9. The process according toclaim 8 wherein the initiator is present in the range of from 0.01 to0.05 moles of initiator per kg of the polypropylene homopolymer orcopolymer.
 10. The process according to claim 1 wherein there is noadded monoene monomer and the initiator is selected from the groupconsisting of Dibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, o,o′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide,m,p′-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (allisomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl)peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers),Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide(all isomers), Bis(octylbenzoyl) peroxide (all isomers),Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide(all isomers), Bis(ethoxybenzoyl) peroxide (all isomers),Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide(all isomers), Bis(pentoxybenzoyl) peroxide (all isomers),Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl)peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers),Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide(all isomers), Bis(fluorobenzoyl) peroxide (all isomers),Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide(all isomers), Bis(trimethylbenzoyl) peroxide (all isomers),Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tertbutoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide (all isomers),Bis(2,4-dimethyl-6-trimethylsilyl benzoyl) peroxide and isomerstert-amyl perbenzoate, tert-amyl (methyl)perbenzoate (all isomers),tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate(all isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl(methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (allisomers), tert-amyl (nonyloxy)perbenzoate (all isomers),Bis(tertamylmonoperoxy phthaloyl) diperoxy terephthalate, diacetylphthaloyl diperoxide, dibenzoyl phthaloyl diperoxide,bis(4-methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl diperoxide and dibenzoyl terephthaloyl diperoxide.
 11. The processaccording to claim 10 wherein the initiator is selected from the groupconsisting of dibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, M,M′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide, andm,p′-Bis(methylbenzoyl) peroxide.
 12. The process according to claim 1wherein the initiator is used in combination with a monoene monomer. 13.The process according to claim 12 wherein the amount of monoene monomeris up to 5 times the total moles of initiator.
 14. The process accordingto claim 12 wherein the monoene monomer is styrene.
 15. The processaccording to claim 12 wherein the initiator is selected from the groupconsisting of Dibenzoyl peroxide, o,o′-Bis(methylbenzoyl) peroxide,p,p′-Bis(methylbenzoyl) peroxide, M,M′-Bis(methylbenzoyl) peroxide,o,m′-Bis(methylbenzoyl) peroxide, o,p′-Bis(methylbenzoyl) peroxide,m,p′-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (allisomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl)peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers),Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide(all isomers), Bis(octylbenzoyl) peroxide (all isomers),Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide(all isomers), Bis(ethoxybenzoyl) peroxide (all isomers),Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide(all isomers), Bis(pentoxybenzoyl) peroxide (all isomers),Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl)peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers),Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide(all isomers), Bis(fluorobenzoyl) peroxide (all isomers),Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide(all isomers), Bis(trimethylbenzoyl) peroxide (all isomers),Bis(tert-butylbenzoyl)peroxide (all isomers),Bis(di-tert-butylbenzoyl)peroxide (all isomers),Bis(tert-butoxybenzoyl)peroxide (all isomers),Bis(ditrimethylsilylbenzoyl) peroxide (all isomers),Bis(heptafluoropropylbenzoyl) peroxide(all isomers),Bis(2,4-dimethyl-6-trimethylsilyl benzoyl) peroxide and isomers,2,2′(dioxydicarbonyl) bis—Benzoic acid dibutyl ester, tert-butylperbenzoate, tert-butyl (methyl)perbenzoate (all isomers), tert-butyl(ethyl)perbenzoate (all isomers), tert-butyl (octyl)perbenzoate (allisomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-amylperbenzoate, tert-amyl (methyl)perbenzoate (all isomers), tert-amyl(ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (allisomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl(methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (allisomers), tert-amyl (nonyloxy)perbenzoate (all isomers), 2-ethylhexylperbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers),2-ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl(octyl)perbenzoate (all isomers), 2-ethylhexyl (nonyl)perbenzoate (allisomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2-ethylhexyl(ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perbenzoate(all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers),Bis(tertbutylmonoperoxy phthaloyl) diperoxy terephthalate,Bis(tertamylmonoperoxy phthaloyl) diperoxy terephthalate diacetylphthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide,dibenzoyl terephthaloyl diperoxide andPoly[dioxycarbonyldioxy(1,1,4,4-tetramethyl-1,4-butanediyl)] peroxide.16. A modified polypropylene produced according to claim
 1. 17. Aprocess wherein the modified polypropylene of claim 16 is melt mixedwith an unmodified polypropylene to produce a modified polypropylene.18. A process for modifying an α-olefin polymer wherein said processcomprises melt mixing the α-olefin polymer in the presence of aninitiator and optionally a monoene monomer wherein said initiator isselected from the group defined by formula 1;

wherein R is selected from the group consisting of optionallysubstituted C₁ to C₁₈ acyl, optionally substituted C₁ to C₁₈ alkyl,aroyl defined by formula 2,

and groups of formula 3,

wherein U, V, X, Z, U′, V′, X′, Y′ and Z′ are independently selectedfrom the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl,aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4,

and wherein T is alkylene; and wherein the amount of monomer is 0 to 3times the total moles of initiator.
 19. A process for increasing themelt strength and/or the extensional melt viscosity of a polypropylene(co)polymer, the process comprising melt mixing a polypropylene(co)polymer in the presence of an initiator and styrene wherein saidinitiator is selected from the group defined by formula 1:

wherein R is selected from the group consisting of optionallysubstituted C₁ to C₁₈ acyl, optionally substituted C₁ to C₁₈ alkyl,aroyl defined by formula 2,

and groups of formula 3,

wherein U, V, X, Y, Z, U′, V′, X′, Y′ and Z′ are independently selectedfrom the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl,aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4,

and wherein T is alkylene, and where styrene is up to five times thetotal moles of initiator; wherein the melt strength and/or theextensional melt viscosity of the polypropylene (co)polymer is increasedduring the melt mixing step.